A soldier patrolling near Kunduz in northern Afghanistan. One incident in which scores of Afghan civilians died prompted an outcry that forced the defence minister to resign. Photograph: Michael Kappeller/AFP/Getty

The German defence ministry is to make a decision in the coming weeks on whether to follow the western military trend and order combat drones armed with air-to-ground missiles, but the issue has come up against persistent ambivalence, 70 years on from the second world war, about the ethics of going into battle.

Writing in Der Spiegel, essayist Dirk Kurbjuweit, warned that "humane" drones could actually be "the most brutal weapons of all" and drew on a still raw memory from Germany's recent military past: a 2009 air strike ordered by a German colonel in Afghanistan that led to the death of 100 Afghans, many of them civilians.

Unwilling to risk German lives, the colonel, Georg Klein, relied on aerial images to call on US warplanes to open fire on two petrol tankers stolen by the Taliban. Kurbjuweit wrote: "If a patrol had been sent, the soldiers would have seen that the trucks were stuck in the mud and no longer posed a threat, and they would also have seen that the people surrounding the trucks were harmless villagers and not combatants. But that would have meant risking German lives, which Colonel Klein didn't want to do."

The killing of scores of civilians, including many children, marked one of the worst death tolls from a single incident in Afghanistan for many years. It had a particularly deep impact on German public opinion, in which the sense of guilt over the Nazi era is still a powerful psychological factor. The defence minister then, Franz Josef Jung, had to resign.

Klein himself, however, was not charged and last month was promoted to the rank of general. The armed forces, the Bundeswehr, shrugged off the hail of criticism.

No western society wants to see troops on the street, but such a domestic role had hitherto represented a particular taboo in Germany because of the country's burden of history. Emerging from the ruins of the war, the post-Nazi German state bound its army tightly in constitutional red tape in the hope it would never again represent a threat to its own people and the rest of Europe.

Over the past two decades there has been a cautious removal of those bonds, one taboo at a time. When war broke out in the Balkans, many Germans argued that the country had a special duty to stop genocide. When Nato finally intervened in 1995, German soldiers were deployed abroad for the first time since the second world war, establishing a military hospital in the Croatian port of Split.

Germany went a step further in Kosovo, where German soldiers fired their first shots in anger, although the mission was peacekeeping again, with an only slightly higher level of danger than Bosnia.

When Germany agreed to contribute troops to Afghanistan three years later, in solidarity with the United States after the 9/11 attacks, the deployment was thought to be only slightly more perilous. In the more peaceful north, Germans were told their soldiers would spend their time helping with development projects. To limit casualties, the deployment was ring-fenced by "caveats" limiting what the soldiers were allowed to do, reportedly provoking a British officer to describe the Bundeswehr as "an aggressive camping organisation".

However, the drastic deterioration in the security situation in the northern provinces where the Germans are garrisoned has forced the caveats to be steadily suspended. In February 2010 the foreign minister, Guido Westerwelle, freed the Bundeswehr further, formally reclassified the Afghan war as "an armed conflict under international law" to allow German soldiers in Afghanistan to act without fear of prosecution on their return home.

"Afghanistan turned out a lot less safe than they thought it was going to be, but the Germans toughed it out, changed their rules of engagement, and fired back," said Tomas Valasek, the director of foreign policy and defence at the Centre for European Reform.

"Germany has gone from a special case to a normal military. It used to be an outlier. Now it is still one of the more reluctant countries in Europe to deploy force, but it's no longer off the charts."

That residual reluctance made itself apparent when the German chancellor, Angela Merkel, and Westerwelle decided to opt out of the Nato intervention in Libya, fearing that a German role in another foreign venture with an uncertain outcome would go down badly with the electorate on the eve of regional elections.

"This was a calculation by individuals in the political class in view of the coming election," Christian Mölling, of the German Institute for International and Security Affairs, said. "I don't think it represented in any way a strategic judgement. Basically thinking about the strategic impact of these moves has not been widespread in Germany."

Ulrike Guérot, of the European Council on Foreign Relations, argued that in retrospect, German abstention from the UN resolution authorising intervention, and its decision not to take part in operations, was a mistake.

"While its closest partners and allies embrace and nurse their commitment to the doctrine of responsibility to protect, Germany still likes to think of itself in terms of that bigger version of Switzerland. But this simply does not work for Europe as a whole," Guérot wrote.

In a German Marshall Fund Ttransatlantic trends poll, more than half of the Germans asked thought that the Libya intervention was justified. Some German military analysts argue such limited operations providing air cover for a limited time in support of a friendly force on the ground provides a far better model for western interventions than the quagmires of Iraq and Afghanistan.

Constanze Stelzenmüller, a security expert at the German Marshall Fund, said: "There is a general dissatisfaction with stabilisation operations, and an approval of quick-in and quick-out, involving air cover and special forces."

By transforming itself into a lighter, more agile expeditionary force that could take part in such operations, the Bundeswehr is now converging organisationally with its European and American partners. Psychologically, however, it may be still be some time before Germans lose their legacy of unease with their armed forces altogether.